I don’t work with regular expressions very often, so I find myself having to brush up on the nuances from time to time. And it gets old writing email validation expressions again and again and again.

So, it was a delightful surprise to stumble across RegExLib. It contains almost a thousand ready-to-go expressions — type in a search term & you view all matching expressions, sorted by ranking. It also has a section where you can test regular expressions, either those from the site or your own. So you can plug away until you find just the right expression to use in your code.